They have three main trolley routes around the main perimeter of the downtown city area; Bay St, Beaver St. and Riverside. The trolley stops are about every 6-8 blocks, and the routes are 4-5 miles one way out of the city. They are free of charge to ride.
You need to check the ride times, but usually they come by every 15 minutes in peak times, and 30 minutes at other times. The times to ride vary for each line, and run 6AM -7PM but Riverside is 10:30-2:30PM weekdays and 8-7 SAturday.